I made an example like you posted outside of my rails app, I have included the zip file with the exact files i am testing in it. When I view that in Chrome or on my Andriod phone it looks like this. I am using Ubuntu 11.10 if that helps, but like I said it looks the same on my Android phone. To use my example all you have to do is extract it and add ST2 in a directory named touch inside the extracted example directory.

Yes I am using PR2 for sure, just to verify my sanity I downloaded it when I posted my last example . In your screen shot the tab panel content is not shown like my original bug report. Then you said to add layout: 'fit' to the viewport, which adds the tab panel to the right of the viewport panel like in the screenshots I provided.

I mean do you guys only test in OSX and on IOS? That would explain why there is a million bugs in EXTJS 4 and ST2.

FWIW i also tested on Chrome and Ubuntu 11.04 at my office with that example you gave with the same result. If I remove layout: 'fit' from the viewport then the content of the tab panel does not show. If I put layout: 'fit' on the viewport it then puts the tabpanel to the right of the viewport exactly the same size. Certainly seems like a bug to me.